1. Field of the Invention
The present invention relates to a powder beam working system, and more specifically, to a powder beam working system being suitably applied to powder beam workings such as etching of a surface to be worked of a work (an object which is to be worked) by projecting a solid-gas two-phase flow which contains fine particles in particular to the surface to be worked.
2. Description of the Related Art
There is conventionally known a powder beam working system of this kind which is configured as shown in FIG. 1.
In a powder beam working system 1 configured as shown in FIG. 1, supplied high-pressure air Air is dried in a dry unit 3 of a solid-gas two-phase flow producing section 2, input by way of a flow rate sensor 4 into a brancher 5 and branched, one obtained high-pressure air (hereinafter referred to as a first branched high-pressure air) Air.sub.1 is given by way of a regulator 6 into a lower portion of a mixing tank 7 and the other high-pressure air (hereinafter referred to as a second branched high-pressure air) Air.sub.2 is given by way of a flow rate controller 8 into an ejector 9.
Fine particles P, for example, of silicon carbide, alumina, glass or the like are accumulated in the mixing tank 7, blasted up by the first branched high-pressure air Air.sub.1 which is supplied from the brancher 5 and supplied by way of a pipe 10 into the ejector 9 in a solid gas state (a condition where the particles are dispersed in the air).
The ejector 9 mixes the second high-pressure air Air.sub.2 which is supplied from the flow rate controller 8 with the fine particles P which are supplied from the mixing tank 7 and sends a solid-gas two-phase flow Air.sub.3 thus obtained under pressure by way of a pipe into a projecting nozzle 12 disposed in a working chamber 11. At this stage, a flow rate of the second branched high-pressure air Air.sub.2 given to the ejector 9 is controlled by the flow rate controller 8 so that a flow rate of the solid-gas two-phase flow Air.sub.3 sent under pressure into the projecting nozzle 12 is constant.
Accordingly, the powder beam working system 1 is capable of blasting the solid-gas two-phase flow Air.sub.3 which is produced by the solid-gas two-phase producing section 2 by way of the projecting nozzle 12 to a surface to be worked of a work 13 which is set in a predetermined condition at a predetermined location in the working chamber 11. Thereby performing etching or a similar working of the surface to be worked of the work 13 with the fine particles P contained in the solid-gas two-phase flow Air.sub.3.
The projecting nozzle 12 is fixed to a tip portion of an arm 15 which is coupled with an XY stage 14 so that it is freely movable in X and Y directions on the basis of propelling forces given in the X direction (indicated by an arrow x) and the Y direction (indicated by an arrow y) from the XY stage 14 by way of the arm 15. Accordingly, the powder beam working system 1 is capable of performing the powder beam working over the entire surface of the work 13.
On the other hand, the working chamber 11 is communicated with a separating chamber 17 by way of a pipe 16 and the solid-gas two-phase flow Air.sub.3 which is projected from the projecting nozzle 12 is sent into the separating chamber 17 through the pipe 16. A portion of the solid-gas two-phase flow Air.sub.3 which is sent into the separating chamber 17 is filtered by a primary filter 18 and then sent back into the working chamber 11 through a pipe 19, whereas the rest is further filtered by a secondary filter 19 which consists of a paper filter and then exhausted outside.
Further, the fine particles P which are separated from the solid-gas two-phase flow Air.sub.3 by the primary filter 18 are sent by way of an openable communicating portion 21 into a storing chamber 22 by a butterfly valve 20.
Disposed in a lower portion of the storing chamber 22 is a screw 23, which is rotated on the basis of a rotating force given from a motor 24, thereby being capable of sending the fine particles P from the storing chamber 22 into the mixing tank 7 of the solid-gas two-phase flow producing section 2 by way of an isolator 25.
Accordingly, the powder beam working system 1 is capable of returning the fine particles P which are used for powder beam working again into the mixing tank 7 sequentially by way of the working chamber 11, the separating chamber 17 and the storing chamber 22, thereby being capable of efficiently using the fine particles P.
In the powder beam working system 1, disposed under the mixing tank 7 is an electronic balance 26 for measuring weight of the fine particles P accumulated in the mixing tank 7 and arranged in an upper portion of the mixing tank 7 is a triangular valve 28 which goes up and down on the basis of propelling forces given from a driving mechanism 27, thereby being capable of opening and closing an inlet port of the mixing tank 7.
Accordingly, the powder beam working system 1 is capable of mechanically separating the storing chamber 22 and the mixing tank 7 from each other with the triangular valve 28. Thereby being capable of sending out the fine particles P always at a constant rate into the ejector 9 while accurately measuring weight of the fine particles P accumulated in the mixing tank 7 with the electronic balance 26.
When it is desired to slightly work the surface to be worked of the work 13 in the powder beam working system 1 having the configuration described above, for example, it is sufficient to reduce a flow rate of the solid-gas two-phase flow Air.sub.3 projected from the projecting nozzle 12 so that the fine particles P which have low kinetic energies collide with the surface to be worked of the work 13.
In order to enhance a working rate in this case, it is sufficient to allow the solid-gas two-phase flow Air.sub.3 to contain the fine particles P in a number as large as possible and it is sufficient in this case to supply the first branched high-pressure air Air.sub.1 at a rate as high as possible into the mixing tank 7.
However, a flow rate of the solid-gas two-phase flow Air.sub.3 projected from the projecting nozzle 12 and a number of the fine particles P contained in the solid-gas two-phase flow Air.sub.3 cannot be adjusted individually in the powder beam working system 1 having the configuration described above, wherein the supplied high-pressure air Air is branched by the brancher 5, the fine particles P accumulated in the mixing tank 7 are blasted up by the first branched high-pressure air Air.sub.1 thus obtained and the solid-gas two-phase flow Air.sub.3 is produced by mixing the fine particles P with the second branched high-pressure air Air.sub.2.
Accordingly, the powder beam working system 1 is incapable of allowing the solid-gas two-phase flow Air.sub.3 to contain the fine particles P in a number as large as possible while suppressing a flow rate of the solid-gas two-phase flow Air.sub.3, thereby posing a problem that it is incapable of coping with use for various kinds of powder beam workings such as the slight working of the surface to be worked of the work 13 at a high working rate.
When a flow rate of the first branched high-pressure air Air.sub.1 to be supplied into the mixing tank 7 is enhanced to allow the solid-gas two-phase flow Air.sub.3 to contain the fine particles P in a number as large as possible (i.e., to enhance a working rate) in the powder beam working system 1 which has the configuration described above, it poses another problem that lumps of the fine particles P (hereinafter referred to as powder balls) are produced and blasted to the surface to be worked of the work 13 by way of the second branched high-pressure air Air.sub.2 in the ejector 9 and the projecting nozzle 12, thereby producing adverse influences not only on the suppression of fine particles projected from the projecting nozzle 12 but also on the work 13 itself.